Engines sometimes use fuel injection systems to introduce fuel into the combustion chambers of the engine. The fuel injection system may be of various types and may include within the system a number of fuel injectors. A fuel injector may include, among the various valves controlling the flow of fuel, solenoid operated valve assemblies. A solenoid operated valve assembly may include a solenoid and an associated valve. The solenoid may include a solenoid coil which acts as a magnet when provided with current, an armature, and a biasing spring.
When the solenoid coil is provided with current, a toroidal field of magnetic flux develops rapidly. While ideally confined to the solenoid coil itself, in reality the magnetic flux tends to fringe into other components, such as, for example, the biasing spring. Relative movement between the electrically conductive biasing spring and the magnetic field may result in an induced voltage in the biasing spring. The induced voltage may result in current flow through valve members of the solenoid controlled valve assembly. Relative movement of cooperating valve members may then cause arcing, which may result in pitting of one or more of the valve members.
At least one system has been developed for mitigating pitting that can occur on a valve seat of a valve when current flows through valve members and the valve is opened. For example, U.S. Pat. No. 4,341,196 (the '196 patent) issued to Canup, et al. on Jul. 27, 1982, discloses a system for purposefully directing current through a fuel injection nozzle valve. Opening the valve breaks current flow to generate a control signal for initiating ignition in an engine. Particularly, the system of the '196 patent provides an electrical circuit means for limiting both voltage and current flow at the valve seat in order to avoid breakdown of a fuel insulating layer and pitting of the valve seat.
The system of the '196 patent may be effective for avoiding pitting in the particular context of a purposefully generated current flow intended to effectuate the generation of an ignition signal. However, introduction of electrical circuitry along the lines disclosed in the '196 patent in a solenoid operated valve assembly to control an unwanted electrical circuit could be ineffective from a cost standpoint. The system may also be complicated to effectively design and implement.
The disclosed apparatus and method help to overcome one or more of the shortcomings in existing technology.